This study was undertaken to find a reliable means of correlating Upper Devonian and Lower Mississippian formations in the Upper Mississippi Valley. Well preserved late Devonian and early Mississippian conodont faunas in the Mississippi Valley have been known for over twenty-five years. Most of these faunas have been described from isolated formations and little attention has been paid to the relationship of faunal assemblages to associated stratigraphic units. Recent studies of sequence of conodont faunal assemblages in other areas, notably in Europe, strongly suggests conodonts may be unexcelled as index fossils in the Upper Devonian and Lower Mississippian. All stratigraphic units assigned to the Kinderhook Series have been sampled for conodonts. Nine distinct faunal assemblage zones are defined ... Conodont faunas described by other workers have been restudied and their relationship to the faunal zones of the reference section is established. The field work was started in the summer of 1955, continued intermittently during the next two years, and was completed in the Spring of 1958.